One of the unconfirmed Avengers: Doomsday castings is that of Tom Holland's Peter Parker. The Spider-Man: Brand New Day post-credit scene is subject to fan speculation that suggests Spider-Man is involved in Battleworld, but it is unclear if Peter Parker is involved in Doomsday or if he will directly appear in Avengers: Secret Wars. But a new fan theory suggests that Holland's Peter Parker will be in Doomsday.This theory suggests that Peter Parker could be the ultimate savior of the entire MCU going forward. Peter's status as a savior is solely due to Doctor Strange's Runes of Kof-Kol spell from Spider-Man: No Way Home. That spell erased people's memory of Peter Parker, and that hasn't been undone in Brand New Day. Therefore, this spell might play a role in Avengers: Doomsday or Secret Wars.Avengers: Doomsday theory: The Runes of Kof-Kol spell shields Peter's existence from Doom's magicMUTATE™ @Goldenstories2LINK🚨Marvel Studios wants us to believe that Doctor Doom’s multiversal crusade is a completely unstoppable sweep, that Victor Von Doom has calculated every move, outmaneuvered the TVA, and positioned himself to wipe out the Avengers across every timeline.But what if the Russo Brothers and Robert Downey Jr. have already dropped the key to Doom’s defeat in plain sight?Look closely at the dual promotional artwork pieces making waves online.RDJ shared a poster featuring a shattered chessboard where every piece has fallen except for a single King piece casting Doom’s shadow. Shortly after, the Russo Brothers posted a celebration featuring Spider-Man wearing the Infinity Gauntlet and holding that exact same King chess piece.And here's where things get interesting.In RDJ’s artwork, a tiny spider stands directly on the board, facing the King piece amidst the fallen wreckage.In the Russo Brothers’ promo art, Spider-Man is physically holding that same King piece in his palm while wearing the Gauntlet.Coincidence? Perhaps. But the symbolism is difficult to ignore.Following the memory-wiping spell at the end of No Way Home, Peter Parker exists as a ghost to the universe.While Doom’s surveillance network calculates strategies against Doctor Strange, Reed Richards, and the Avengers, he cannot calculate for a hero whose identity was wiped from reality.Peter Parker is the one piece not on Doom’s board.And this could set up a profound emotional payoff for Tom Holland’s character arc.THE STAND: Doctor Doom sits upon his throne on Battleworld, convinced that every hero who challenged him has been removed from the board.THE REVEAL: A shadow falls over the throne room as Spider-Man steps out of the dark, holding the core key to Doom's power engine.THE PAYOFF: From being mentored by Tony Stark to outsmarting the man who wears Stark’s face, Peter Parker turns his greatest curse, being forgotten by the world, into the ultimate weapon to save the multiverse.Think about that for a moment.The hero everyone forgot could become the one person Doom never saw coming.Do you believe it? Is Spider-Man the secret piece destined to checkmate Doctor Doom, or is this just clever promotional art?The trailers for Avengers: Doomsday suggest that Doom is the superhero team's greatest challenge to date. If the movie follows the comics, we can expect Doom to be both a sorcerer and a scientist. Thus, the theory suggests that even if Doom were to win in Doomsday, the Avengers have one trump card up their sleeve. Spider-Man.Strange's Runes of Kof-Kol spell ensures that no one in the MCU knows that Peter is Spider-Man. The new theory suggests that Peter manages to keep his identity a secret in Doomsday, and he is one of the few heroes to survive Doom's rewriting of reality.Much like the "dead man's spell" in Avengers: Infinity War, the Runes of Kof-Kol could be another spell of Strange that's sneakily powerful. The only difference is that it could shield Peter from Doom's magic. The Russos even teased something similar back in August.In July, RDJ (Robert Downey Jr.) shared an artwork by popular artist BossLogic in his stories. The fanart of Avengers: Doomsday featured a chessboard with a king piece (representing Doom) standing victorious, surrounded by destruction. However, there is a spider standing right opposite the king piece (representing Spider-Man).RDJ teasing the plot? | Image Via: Instagram/@robertdowneyjrJust a month later, the Russo Brothers posted a congratulatory post dedicated to the Spider-Man: Brand New Day team. It featured an image of the Wall-Crawler wearing the Infinity Stones in the ring form in one hand and holding the same king chess piece on the other. View this post on Instagram Instagram PostThis new fan theory combines these two things and suggests that Spider-Man will be the one hero to beat Doom. If this were true, this defeat would be a full-circle moment for Peter's character arc in the entire MCU. He started the MCU as the prodigy of Tony Stark, and it would make sense for Parker to be the downfall of the man who has his mentor's face.However, the question still remains.Is Tom Holland's Peter Parker a part of Doomsday?"Spider-Man: Brand New Day" Fan Event - Source: GettyAs of now Holland has not been officially confirmed to appear in the movie. There are conflicting reports about his involvement in Doomsday. The Spider-Man: Brand New Day post-credit scene ties into Avengers: Secret Wars. Therefore, it would make sense that Holland appears in Secret Wars. However, we don't know if Tom Holland is in Avengers: Doomsday.If his character is to make sense in Avengers: Secret Wars, he needs to have a cameo in Doomsday.What do we need to know about Doomsday?The Doomsday poster | Image Via: Instagram/@barco.cinemaThe upcoming Avengers movie releasing next month will follow the team trying to solve the issue of incursions. Leaks have suggested that Doom starts the movie as an ally only to turn the tables by betraying everyone. Also involved in the movie are heroes of three different universes. The official logline alludes to the Avengers, Fantastic Four, and the X-Men collaborating to solve incursions:"'Avengers: Doomsday' follows beloved heroes from three distinct universes as they’re set on a deadly collision course and face an existential threat unlike anything they’ve ever encountered."The movie releases in theaters across the US on December 18, 2026. Book your tickets if you haven't already.